The present invention relates to a device for regulating the rate of flow of water comprised of waste water mixed with clear rainwater to a purification station. The invention is particularly useful for handling water flow during or after a flood or a storm. The device is of the type comprising a collector chamber equipped with a first orifice for receiving the mixed water, a second orifice for discharging water containing a higher concentration of waste water, and a third orifice for discharging water containing a higher concentration of clear water. The collector chamber contains an adjustable device for directing a predetermined quantity of water which has a higher concentration of waste water toward the second orifice and for discharging the remaining water containing a higher concentration of clear water into the collector chamber and toward the third orifice.
Following a storm, the rate of flow of mixed waste water and rainwater can be greater than 100 times the rate of flow measured in dry weather. Purificiation stations are generally designed to treat at most twice the dry-weather rate of flow. The specifications for sewers are based at present on a specific dry-weather rate of flow of 0.01 liter/sec. per inhabitant.
In order to eliminate the excessive waste water which is heavily diluted by rainwater, flood weirs or storm weirs, each in the form of a dam with an overflow crest, i.e. a dam surmounted by an overflow crest followed by a charge section, or an overflow dam with charge sections upstream and downstream, are provided at suitable points. Flood weir dams are able to retain surplus water to a certain extent. At least temporarily, there is settling of the mixed water, because the heavier waste water has a tendency to pass to the bottom while the clear water, heavily diluted by rainwater, tends to stay at the upper level. However, precise adjustment of the rate of flow of the waste water fed to the purification station is difficult, and flood weirs have the major drawback of making it impossible to maintain the rate of flow of the water transmitted to a purification station within acceptable limits in case of a sudden flood, in particular after a storm.
Generally, dynamic flow regulating devices of the above-mentioned type do not permit precise regulation of the rate of flow. The rate of flow at the time of floods or after a storm, as noted above, is far greater than twice the value of the rate of flow in dry weather. Furthermore, the turbulence of the entering stream prevents the mixed water from effectively settling, with the result that it is difficult to ensure that only water which has a higher concentration of waste matter is sent to the purification station.